In the field of computer aided design and manufacturing, geometric modeling systems, such as PADL-2 marketed by Cornell University are available for generating structurally complex three dimensional models. These models are normally constructed in a series of steps which include first developing a sharp edged dimensionally accurate solid model. Depending upon the complexity of the model, the time required to produce the solid model varies from hours to months. For example, a part of moderate complexity, such as a die model for a track link forging, requires approximately one month of experienced operator input to complete.
Secondly, it is necessary to replace the undesirable sharp edges and corners with blends of selected radii. This is particularly important when the model is a forging die. Forgings with sharp edges tend to have stress risers concentrated at the sharp edges and will resultantly have a greater likelihood of failure. Furthermore, the blended aspect improves the flow of hot metal as it assumes the shape imposed by the die. Presently available systems typically accomplish blending as a local modification operation requiring extensive user input. In the track link forging example, this local blending process required nearly three months of operator input. Further, system vendor attempts to partially automate the local blending process have not been entirely successful.
There is a practical limit to the complexity of the model which can be blended using local modification methods. In automated local modification methods, the junction of multiple edges must be treated by example. The method must specifically address how the junction should appear for each variation in number of edges, angle between edges, and blend radius. The variety of corners and other detail is readily apparent and any attempt to treat all possible combinations would prove to be impractical.
The present invention is directed to overcoming one or more of the problems as set forth above. In particular, a method of global blending which reduces the need for user interaction and is not subject to limitations in model complexity is desirable.